This invention relates to radar systems, and more particularly, to a noise discriminating, continuous wave (CW), pseudonoise radar.
In the past, the problem of discriminating against spillover and other noise has been recognized. See copending application Ser. No. 880,057, now U.S. Ser. No. 3,641,573, filed Nov. 26, 1969, by D. F. Albanese for PSEUDONOISE RADAR SYSTEM and assigned to the assignee of the present application.
In determining the range of a moving target, a CW radar is often used, including a transmitter having a transmitting antenna and a receiver having a receiving antenna. Electromagnetic energy transmitted directly from the transmitter to the receiver is unwanted because the wave reflected from the target is that from which range is determined. This directly transmitted energy is thus noise and is called spillover.
Spillover can be partially attenuated in a pseudonoise radar system by decoding the incoming wave by a code delayed an amount directly proportional to the distance between the transmitting and receiving antennas. Then, by the use of a notch filter or D.C. blocking capacitor, a large portion of the spillover may be suppressed without substantially attenuating the wave reflected by the target.
Notwithstanding the foregoing, enough of the spillover energy is still left and is quite troublesome.
In prior art systems, it has been impossible to separate spillover and other noise from the desired signal other than by the means described above. This has been due to the character of the power spectrum of the spillover, which spectrum normally has lines which fall close to, on both sides of, and directly on those of the desired signal.